Electrical switching system

ABSTRACT

An electrical switching system especially adapted to control a blower and heating elements in a heating system for an enclosure for sequentially actuating the blower and heating elements, including a thermostat for sensing the temperature within the controlled enclosure, an electrical resistance-type pilot heater connected with and controlled by the thermostat, and a plurality of thermal switches actuated in response to the pilot heater, each of the thermal switches being activated at a different temperature for sequentially supplying power to a blower and to electrical resistance heating elements for heating air coupled with the thermal switches. In a preferred form of the switching system a single pilot heater activates two thermal switches, one being connected to a blower and a first electrical resistance heater initially turning on the blower and the heater while the other thermal switch is connected to second and third electrical resistance heaters for turning on such heaters after a predetermined time and temperature delay.

United States Patent 1 [111 3,852,695 Northrup, Jr. Dec. 3, 1974 1 ELECTRICAL SWITCHING SYSTEM I [76] Inventor: Leonard L. Northrup, Jr., 4312 [57] ABSTRACT Westway, Dallas, Tex. 75205 An electrical switching system especially adapted to [22] Filed p 9 1973 control a blower and heating elements in a heating [21] Appl. No.: 349,253

Primary Examiner-R. Skudy Assistant ExaminerFred E. Bell Attorney, Agent, or Firm-H. Mathews Garland system for an enclosure for sequentially actuating the blower and heating elements, including a thermostat for sensing the temperature within the controlled enclosure, an electrical resistance-type pilot heater connected with and controlled by the thermostat, and a plurality of thermal switches actuated in response to the pilot heater, each of the thermal switches being activated at a different temperature for sequentially supplying power to a blower and to electrical resistance heating elements for heating air coupled with the thermal switches. In a preferred form of the [52] US. Cl. 337/102, 337/40;96;l03;336;373 i [51] Int. Cl. I-I0lh 61/00 [58] Field of Search 337/40, 95, 96, 102, 103, 337/104, 105, 107, 336, 371

[56] References Cited UNITED STATES PATENTS 1,655,967 1/1928 Matthews 337/96 2,506,272 5/1950 Koci 1 337/96 X 2,658,175 11/1953 Clark l 337/40 X 3,551,868 12/1970 ,Good 337/102 X 3,718,879 2/1973 Perry 337/102 X switching system a single pilot heater activates two thermal switches, one being connected to a blower and a first electricalresistance heater initially turning on the blower and the heater while the other thermal switch is connected to second andthird electrical resistance heaters for turning on such heaters after a predetermined time and temperature delay.

10 Claims, 6 Drawing Figures 1 45 5/ 34 5n l J L J 34 43V -1 aa 745/5 E W 0 3 I K 3. 6] I l j 12 i *iHTl/E) l 6/ 62 6'0; 1 62 L. T 1 g 7 34 b /4 2 1 1 4 LZVFZHHWI 43mm 57' 4 PAIENIEB BEE mraur ELECTRICAL SWITCHING SYSTEM This invention relates to electrical switching systems and more particularly relates to an electrical switching system for sequentially controlling a plurality of electrically energized components.

In accordance with the invention, there is provided an electrical switching system for sequentially activating electrically energized components in response to the sensing of a predetermined condition, such as a temperature. The switching system includes an electrical resistance-type pilot heater activated by temperature sensing means, such as a room thermostat, and a plurality of thermal switches supported in close proximity to the pilot heater and operable at different temperatures for sequentially energizing electrical components connected with the thermal switches. The pilot heater is preferably-energized by a safe low voltage while the thermal switches are adapted to carry full line current for supplying electrical energy to electrical components, such as electrical resistance heaters and a blower in heating systems for heating air in enclosures. g

It is an especially important object of the invention to provide a new and improved electrical switching system.

It is another object of the invention to provide a new and improved electrical switching system. for sequentially activating a plurality of electrical switches responsive to a-single signal.

It is another object of the invention to provide an electrical switching system which-is operable'in response to a single electrical resistance-type pilot heater.

Itis another object of the invention to provide an electrical switching system operable responsive to low voltage for controlling higher, full line voltage.

It is another object of the invention to provide an electrical switching system which includes a plurality of thermal switches for controlling full line voltage, such switches being supported in close proximity to an elec- FIG. 2 is an enlarged view in section taken along the line 2--2 of FIG. 1 illustrating the internal construction of the switching system of the invention;

FIG. 3 is a view in section and elevation along the line 33 of FIG. 2 showingparticularly the pilot heater of the switching system;

FIG. 4 is a view in section and elevation along the line 44 of FIG. 2;

FIG. 5 is a perspective view of a heat-responsive disc with a switch-actuating arm employed in the switching system illustrated in FIGS. 1-4; and

FIG. 6 is a wiring diagramillustrating a particularly preferred use of the switching system of the invention in a heating system having a blower motor and a plurality of electrical resistance heating elements.

Referring to FIGS. l-5, a switching system 10 com prising a preferred form of the invention includes a pair of heat or thermally-responsive electrical switches 11 and 12 coupled together on opposite sides of and in close proximity to a pilot heater 13. The switches 11 and 12 are designed to respond to different temperature levels of heat emitted by the pilot heater 13. Thus, as the pilot heater increases in temperature, the switches 11 and 12 are sequentiallyturned on to supply power to electrical components coupled with the switches, as discussed in further detail hereinafter.

Structurally, the switches 11 and 12 are identical in designand differ only intemperature'value response so switch 11 has a body 14 formed of a suitable electritrical resistance type pilot heater activated by low voltage and adaptedto heat the thermal switches for sequentially activating the switches to turn on all of the switchesat different temperature levels over a short time period.

It is another object of the invention to provide a switching system which is especially adapted to sequentially control a blower motor and a plurality of electrical resistance heaters in an air conditioning system for an enclosure for turning the motors and heaters on in time and temperature-spaced sequences to avoid placingthe entire load on the line instantaneously.

It isanother object of the invention to provide an electrical switching system which permits the control of full line voltage across a blower motor and electrical resistance heaters by means of a safe, low voltage circuit, located within the normal area of activity of an operator of the system.

A more thorough understanding of the invention, together with its objects and advantages, will be evident from reading the following detailed description of the invention taken in conjunction with the drawings" wherein:

FIG. 1 is a perspective view of a switching system constructed in accordance with the invention;

cally insulating plastic material. The body includes an inner hollow cylindrical portion 15 provided with a cavity and an integral outer larger and generally rectangular portion 21 which is slotted at opposite ends at 21a and 21b. Conductor bars 22, 23, 24, and are secured as by bradding to the body portion 21 and extend in shallow slots along the body beneath a cover plate also bradded to the body portion 21. The free ends of the conductor bars project from the body portion 21 for soldering or otherwise suitable connection of leads to the components controlledby the switch system. The conductor bars areconnected within the switch body to suitable movable contacts, not shown,

each pair of which is opened and closed by an operator member in the cavity 20. For example, the conductors 22 and 24 are connected with contacts operated by an operator member 31. Conductor bars 23 and 25 connect with a pair of contacts opened and closed by an operator member 32. When the switch is closed, the

conductors 22 and 24 are electrically connected to form one circuit through the switch 11 while the conductors 23 and 25 are similarly electrically connected to form another circuit through the switch.

The switch body 14 is tightly titted along aninward end portion into a cylindrical case 33 having an external flange 33a with tabs 34 each having an opening or hole 35 for a screw or bolt to secure the switch with a mounting plate, not shown. The case 33 has an internal shown in solid lines in FIG. 2 to an outwardly curving shape as represented by the broken lines of FIG. 2. A

Y-shaped operator 43 is connected at a trunk portion 44 to the center of the disc 42. Upper arm portions 45 and 50 of the operator 43 have heads 51 and 52, respectively, for engagement with adjacent switch contact operator members 31 and 32. When the operator 43 is moved outwardly by the deformation of the disc 42 to an outwardly curving shape as represented by broken lines in FIG. 2, the heads 51 and 52 close the switch, electrically connecting the pairs of contacts coupled with the conductor bars 22, 23, 24, and 25 so that electric circuits are completed along paths defining one'circuit through the conductors 22 and 24 and a parallel separate circuit through the conductors 23 and,25.

The various component parts of the switch 12, which is identical to the switch 11, are numbered with the samereference numerals used in association with the switch 11 with a prime mark added. The bi-metallic heat responsive disc 42' is, however, designed to respond to a temperature different from that to which the disc 42 responds. By way of example, one of the heat responsive discs may deform and close the switches associated with it at a temperature of 200, while the other disc may respond and close the switches coupled with it at a temperature of 225. Both of the thermal switches may be commercially available switches such as sold under the trademark Klixon.

The thermal switches 11 and 12 are secured into opposite ends of a cylindrical, thermal and electrical insulating, open-ended case 60 so that the heat responsive discs 42 and 42' are disposed inwardly while the conductors 22-25 and 222 of the switches are located at opposite ends of the switching system as seen in FIGS. 1 and 2 for connection of the switching system into electrical circuits to be controlled by the system.

tuate the switching system. The pilot heater comprises an electrically insulating core 63 on which is wound an electrical resistance heating wire 64 connected at opposite ends, as seen in FIG. 3, withthe conducting brads 61 for supplying energy to the heating element.

. FIG. 6 illustrates the incorporation of the electrical switching system 10 of FIGS. l-5 in a heating system for an enclosure including electrical resistance heating elements and a blower motor operative by the switching system of the invention responsive to a temperature sensing thermostat. For purposes of correlation between FIG. 6 and FIGS. l-S, those components schematically represented in FIG. 6 which are common to the structure shown in FIGS. l-5 shall be referred to in FIG. 6 by the same reference numerals as used in FIGS. l-5. Referring to FIG. 6, a suitable standard thermostat 70 including a switch 7land a variable resistor 72 is located in an enclosure, not shown, to be heated by the system. The thermostat is connected in a circuit including leads 73 and 74 connected with a secondary 75 of a transformer having a primary 81. Typically, the primary is operated at full line voltage which may be I 15, 208, or 240 volts, while the secondary is operated at 24 volts. The element 64 of the pilot heater 13 is connected at one end with the lead 74 and at the other end with a lead 73' extending to the thermostat 70 whereby the pilot heater is operative at a current of 24 volts responsive to the thermostat. In'the actual connection of the switching system 10 into the circuitry shown in FIG. 6, the leads 73' and 74 are connected with the contacts 62 which engage the opposite ends of the pilot heater element 64. Full line voltage, which typically is 240 volts at 60 cycles, is connected by leads 82 and 83 with the thermal switches 11 and 12 of the switching system 10 and with a blower motor.84 and electrical resistance type heaters 85, 90, and 91. The lead 82 is connected as shown to the contacts at first sides of the thermal switches 11 and 12, while the blower motor and resistance heaters are connected to the other sides of the thermal switches. More specifically, the thermal switch 11 is connected in the circuits between the leads 82 and 83 to the blower motor 84 and one of the electrical resistance heaters 85. Similarly, the other thermal switch 12 is connected in circuits between the leads 82 and 83 extending to the electrical resistance heaters 90 and 91. With this circuit arrangement, the closure of the thermal switch 11 activates the blower motor 84 and the resistance heater 85 while the closure of the switch 12 energizes the resistance heaters and 91.

In the operation of the heating system of FIG. 6, when the temperature in the enclosure in which the thermostat 70 is located reaches a predetermined value at which the thermostat is set to. respond,the thermostat closes completing the circuit from the transformer 80 to the element 64 of the pilot heater in the switching system 10 causing the heating element of the pilot heater to increase in temperature. As the pilot heater temperature rises, the temperature of each of the bimetallic discs 42 and 42' of the switches 11 and I2 is increased. The switches 11 and'l2 are sequentially closed by the heat from the resistance element 64 of the pilot heater. For example, the disc 42 of the switch 11 may be designed to respond to a temperature of 200 while the disc 42' of the switch 12 is designed to respond to a temperature of 225 F. When the disc 42 is elevated in temperature to 200 F. by'the pilot heater, the disc deforms outwardly, as shown in FIG. 2 by the broken line representation of. the disc, moving the operator 43.

outwardly to engage the operator members-31 and 32 in the switch for closing the circuits connected with the conductors 22 and 24, and 23 and 25, therebyturning on the blower motor 84 and energizing the resistance heater 85. Thereafter, as soon as the disc 42 is raised in temperature to 225, the disc deformsoutwardly causing the operator 43 to complete the circuits connected with the switching system conductors 22', 24' 23, and 25', thereby energizing the resistance heaters 90 and 91. Thus, sequential activating of the blower motor and the resistance heating elements is effected by the switching system 10 so that in a short time span, the entire system is in operation without the electrical load of all of the resistance heaters and the blower motor being placed on'the line simultaneously.

Normally, the resistance heaters are within the duct work through which air is delivered by the fan, not shown, driven by the blower motor 84 so that the air directed into the enclosure housing the thermostat 70 is heated. When such air reaches the temperature at which the thermostat is set to cut off, the thermostat 70 opens the circuits to the pilot heater de-energizing the resistance element 64 of the pilot heater allowing the discs 42 and 42 of the thermal switches to cool. When the disc 42 reaches the deformation temperature of 225, it snaps inwardly to the solid line position of FIG. 2 opening the two sets of contacts in the switch 12 deenergizing the resistance heaters 90 and 91. The temperature within the switching system housing continues to decrease and when the disc 42 reaches its deformation temperature of 200 F it returns to the inwardlydished shape shown by solid lines in H0. 2 opening the circuits connected through the switch 11, thereby deenergizing the blower motor 84 and the resistance heater 85.

It will be recognized that a new and improved electrical switching system has been described and illustrated wherein a low voltage circuit is used to energize a pilot heater positioned in close proximity to thermal switches which are adapted to respond at different temperature levels so that various components connected with the switches are sequentially energized, thereby avoiding placing the full load of an entire system in operation at the same instant. The use of a small, lowpower pilot'heater in very close proximity to the thermal switches permits a compact, reliable and economical switching system to be constructedlt will be recognized that while only two thermal switches are shown, the system may include additional switches located to respond to the pilot heater, each of the switches having bimetallic discs designed to operate at different temperatures so that the circuits connected with the several switches in the system are each activated at different times.

What is claimed and desired to be secured by Letters Patent is:

1. An electrical switching system comprising: an electrically activated pilot heater connectible with and responsive to a thermostat; and a plurality of heatresponsive electrical switches supported in spaced relation to saidpilot heater each switch being electrically connected with separate circuits independent of the circuit including said pilot heater for controlling circuit connected with said switches in response to heat sensed by said switches from said pilot heater whereby said circuits connected with said switches are energized and de-energized responsive to the temperature sensed by said thermostat.

2. An electrical switching system in accordance with claim 1 wherein each of said switches is responsive to a different temperature for sequentially energizing and de-energizing circuits connected through said switches.

3. A switching system in accordance with claim 2 5. An electrical switching system in accordance with claim 4 wherein said pilot heater and said deformable discs of said thermal switches are encased within a housing and said deformable discs and said heater are aligned along a common axis substantially perpendicular to said heater and said discs. 4

6. An electrical switching system for controlling a plurality of separate electrical circuits responsive to a single electrical signal from a thermostat in a circuit separate from said controlled electrical circuits comprising: housing means; an electrical resistance pilot heater secured within said housing means and connectible with said circuit including said thermostat; contact means connected through said housing means with said heater for coupling said heater in said electrical circuit including said thermostat for sending said electrical signal to said switching system; a plurality of thermal switches secured in said housing in heat-sensing relationship with said heater and each connected in said separate controlled circuits, each of said switches having a mechanicallydistortable heat-sensitive nonelectrically conducting member and electrical switch contacts coupled with said member for closing and opening said electrical circuits connected with each set of said contacts in said thermal switch; each of said thermal switches in said housing being responsive to different temperatures for opening and closing said switches sequentially responsive to heat generated by said heater; and electrical connecting means secured with each set of contacts in each of said thermal switches for electrically coupling each set of contacts of each of said switches in said separate electrical circuits whereby said circuits are'each controlled by said pilot heater.

7. An electrical switching system in'accordance with claim 6 wherein said pilot heater comprises a substantially flat wound electrical resistance wire, and each of said thermal switches includes a heat-distortable plate for mechanically opening and closing the contacts of each of said switches, said plates being disposed along opposite planar surfaces of said substantially flat pilot heater.

8. An electrical switching system in accordance with claim 7 including two of said thermal switches, one of said switches being on one side of said pilot heater with said plate of said switch being in close spaced relation with said pilot heater and the other of said thermal switches being on the other'side of said pilot heater with said plate of said other thermal switch being disposed in close spaced relation with said other side of said heater. 7

9. An electrical switching system in accordance with claim 8 wherein each of said thermal switches includes two sets of electrical contacts whereby each of said switches is connectiblein and controls two separate electrical circuits.

10. vAn electrical switching system in accordance with claim 9 connected with thermostat means positioned in a space adapted to be air-conditioned by means connected with said separate controlled electrical circuits, said thermostat being electrically connected with said pilot heater of said switching system for energizing said pilot heater responsive to electrical current controlled by said thermostat. 

1. An electrical switching system comprising: an electrically activated pilot heater connectible with and responsive to a thermostat; and a plurality of heat-responsive electrical switches supported in spaced relation to said pilot heater each switch being electrically connected with separate circuits independent of the circuit including said pilot heater for controlling circuit connected with said switches in response to heat sensed by said switches from said pilot heater whereby said circuits connected with said switches are energized and deenergized responsive to the temperature sensed by said thermostat.
 2. An electrical switching system in accordance with claim 1 wherein each of said switches is responsive to a different temperature for sequentially energizing and de-energizing circuits connected through said switches.
 3. A switching system in accordance with claim 2 wherein each of said switches includes a non-electrically conducting bi-metallic disc adapted to distort responsive to heat sensed from said pilot heater.
 4. An electrical switching system in accordance with claim 3 wherein the deformable disc of each of said thermal switches is supported in substantially parallel relationship with said pilot heater.
 5. An electrical switching system in accordance with claim 4 wherein said pilot heater and said deformable discs of said thermal switches are encased within a housing and said deformable discs and said heater are aligned along a common axis substantially perpendicular to said heater and said discs.
 6. An electrical switching system for controlling a plurality of separate electrical circuits responsive to a single electrical signal from a thermostat in a circuit separate from said controlled electrical circuits comprising: housing means; an electrical resistance pilot heater secured within said housing means and connectible with said circuit including said thermostat; contact means connected through said housing means with said heater for coupling said heater in said electrical circuit including said thermostat for sending said electrical signal to said switching system; a plurality of thermal switches secured in said housing in heat-sensing relationship with said heater and each connected in said separate controlled circuits, each of said switches having a mechanically distortable heat-sensitive non-electrically conducting member and electrical sWitch contacts coupled with said member for closing and opening said electrical circuits connected with each set of said contacts in said thermal switch; each of said thermal switches in said housing being responsive to different temperatures for opening and closing said switches sequentially responsive to heat generated by said heater; and electrical connecting means secured with each set of contacts in each of said thermal switches for electrically coupling each set of contacts of each of said switches in said separate electrical circuits whereby said circuits are each controlled by said pilot heater.
 7. An electrical switching system in accordance with claim 6 wherein said pilot heater comprises a substantially flat wound electrical resistance wire, and each of said thermal switches includes a heat-distortable plate for mechanically opening and closing the contacts of each of said switches, said plates being disposed along opposite planar surfaces of said substantially flat pilot heater.
 8. An electrical switching system in accordance with claim 7 including two of said thermal switches, one of said switches being on one side of said pilot heater with said plate of said switch being in close spaced relation with said pilot heater and the other of said thermal switches being on the other side of said pilot heater with said plate of said other thermal switch being disposed in close spaced relation with said other side of said heater.
 9. An electrical switching system in accordance with claim 8 wherein each of said thermal switches includes two sets of electrical contacts whereby each of said switches is connectible in and controls two separate electrical circuits.
 10. An electrical switching system in accordance with claim 9 connected with thermostat means positioned in a space adapted to be air-conditioned by means connected with said separate controlled electrical circuits, said thermostat being electrically connected with said pilot heater of said switching system for energizing said pilot heater responsive to electrical current controlled by said thermostat. 